scholarly journals A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 860 ◽  
Author(s):  
Fu Chen ◽  
Yongzhi Cheng ◽  
Hui Luo
Keyword(s):  
Energy Level ◽  
Graphene Sheet ◽  
Fermi Energy ◽  
Single Layer ◽  
Dielectric Substrate ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Absorption Capacity ◽  
Fermi Energy Level ◽  
Broadband Absorption

We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion-shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef = 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90%, can reaches its maximal value of 72.1%. Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization-insensitive and has wide angles for both transverse-electric (TE) and transverse-magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference 41theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.

scholarly journals Efficient Broadband Truncated-Pyramid-Based Metamaterial Absorber in the Visible and Near-Infrared Regions

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 784 ◽  
Author(s):  
Phuc Toan Dang ◽  
Tuan V. Vu ◽  
Jongyoon Kim ◽  
Jimin Park ◽  
Van-Chuc Nguyen ◽  
...  
Keyword(s):  
Communication Systems ◽  
Near Infrared ◽  
Cell Structure ◽  
Single Layer ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Broadband Absorption ◽  
Polarization Insensitive ◽  
Truncated Pyramid

We present a design of an ultra-broadband metamaterial absorber in the visible and near- infrared regions. The unit cell structure consists of a single layer of metallic truncated-pyramid resonator-dielectric-metal configuration, which results in a high absorption over a broad wavelength range. The absorber exhibits 98% absorption at normal incidence spanning a wideband range of 417–1091 nm, with >99% absorption within 822–1054 nm. The broadband absorption stability maintains 95% at large incident angles up to 40° for the transverse electric (TE)-mode and 20° for the transverse magnetic (TM)-mode. Furthermore, the polarization-insensitive broadband absorption is presented in this paper by analyzing absorption performance with various polarization angles. The proposed absorber can be applied for applications such as solar cells, infrared detection, and communication systems thanks to the convenient and compatible bandwidth for electronic THz sources.

scholarly journals Numerical Investigation of Graphene and STO Based Tunable Terahertz Absorber with Switchable Bifunctionality of Broadband and Narrowband Absorption

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2044
Author(s):  
Yan Liu ◽  
Rui Huang ◽  
Zhengbiao Ouyang
Keyword(s):  
Energy Level ◽  
Fermi Energy ◽  
High Performance ◽  
Thermal Control ◽  
Rate Of Change ◽  
Center Frequency ◽  
Fermi Energy Level ◽  
Broadband Absorption ◽  
Terahertz Absorber ◽  
The Cross

A graphene metamaterial and strontium titanate (STO)-based terahertz absorber with tunable and switchable bifunctionality has been numerically investigated in this work. Through electrically tuning the Fermi energy level of the cross-shaped graphene, the bandwidth of the proposed absorber varies continuously from 0.12 THz to 0.38 THz with the absorptance exceeding 90%, which indicates the functionality of broadband absorption. When the Fermi energy level of the cross-shaped graphene is 0 eV, the proposed absorber exhibits the other functionality of narrowband absorption owing to the thermal control of the relative permittivity of STO, and the rate of change of the center frequency is 50% ranging from 0.56 THz to 0.84 THz. The peak intensity of the narrowband absorption approximates to nearly 100% through adjusting the Fermi energy level of the graphene strips. The calculated results indicate that it is not sensitive to the polarization for wide incidence angles. The proposed absorber can realize tunable bifunctionality of broadband absorption with a tunable bandwidth and narrowband absorption with a tunable center frequency, which provides an alternative design opinion of the tunable terahertz devices with high performance for high-density integrated systems.

Single-peak-regulation and wide-angle dual-band metamaterial absorber based on hollow-cross and solid-cross resonators

2020 ◽  
Vol 91 (3) ◽  
pp. 30901
Author(s):  
Yibo Tang ◽  
Longhui He ◽  
Jianming Xu ◽  
Hailang He ◽  
Yuhan Li ◽  
...  
Keyword(s):  
Transverse Electric ◽  
Surface Current ◽  
Dielectric Substrate ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Absorption Peak ◽  
Dual Band ◽  
Single Peak ◽  
Wide Angle ◽  
Surface Current Density

A dual-band microwave metamaterial absorber with single-peak regulation and wide-angle absorption has been proposed and illustrated. The designed metamaterial absorber is consisted of hollow-cross resonators, solid-cross resonators, dielectric substrate and metallic background plane. Strong absorption peak coefficients of 99.92% and 99.55% are achieved at 8.42 and 11.31 GHz, respectively, which is basically consistent with the experimental results. Surface current density and changing material properties are employed to illustrate the absorptive mechanism. More importantly, the proposed dual-band metamaterial absorber has the adjustable property of single absorption peak and could operate well at wide incidence angles for both transverse electric (TE) and transverse magnetic (TM) waves. Research results could provide and enrich instructive guidances for realizing a single-peak-regulation and wide-angle dual-band metamaterial absorber.

scholarly journals Electrically Tunable Broadband Terahertz Absorption with Hybrid-Patterned Graphene Metasurfaces

Nanomaterials ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 562 ◽  
Author(s):  
Longfang Ye ◽  
Xin Chen ◽  
Guoxiong Cai ◽  
Jinfeng Zhu ◽  
Na Liu ◽  
...  
Keyword(s):  
Incident Angle ◽  
Single Layer ◽  
Normal Incidence ◽  
Transverse Magnetic ◽  
Single Layer Graphene ◽  
Terahertz Waves ◽  
Broadband Absorption ◽  
Terahertz Sensing ◽  
Axisymmetric Configuration ◽  
Broadband Terahertz

We numerically demonstrate a broadband terahertz (THz) absorber that is based on a hybrid-patterned graphene metasurface with excellent properties of polarization insensitivity, wide-angle, and active tunability. Our design is made up of a single-layer graphene with periodically arranged hybrid square/disk/loop patterns on a multilayer structure. We find that broadband absorption with 90% terahertz absorbance and the fractional bandwidth of 84.5% from 1.38 THz to 3.4 THz can be achieved. Because of the axisymmetric configuration, the absorber demonstrates absolute polarization independence for both transverse electric (TE) and transverse magnetic (TM) polarized terahertz waves under normal incidence. We also show that a bandwidth of 60% absorbance still remains 2.7 THz, ranging from 1.3 THz to 4 THz, for a wide incident angle ranging from 0° to 60°. Finally, we find that by changing the graphene Fermi energy from 0.7 eV to 0 eV, the absorbance of the absorbers can be easily tuned from more than 90% to lower than 20%. The proposed absorber may have promising applications in terahertz sensing, detecting, imaging, and cloaking.

Intersubband Transitions in In0.07Ga0.93As/Al0.4Ga0.6As Multiple Quantum Wells

1994 ◽  
Vol 299 ◽  
Author(s):  
F. Szmulowicz ◽  
M. O. Manasreh ◽  
C. Kutsche ◽  
C. E. Stutz
Keyword(s):  
Energy Level ◽  
Quantum Well ◽  
Quantum Wells ◽  
Excited States ◽  
Fermi Energy ◽  
Multiple Quantum Well ◽  
Energy Separation ◽  
Multiple Quantum ◽  
Fermi Energy Level ◽  
Intersubband Transitions

AbstractIntersubband transitions in a series of well-doped ([Si] = 2.0×1018cm−3) In0.07Ga0.93As/Al0.4Ga0.6As multiple quantum well samples were studied as a function of the well width by using the optical absorption technique. A single intersubband transition is observed in samples in which the Fermi energy level is between the ground and the first excited states in the quantum well. On the other hand, two intersubband transitions were recorded in samples where the Fermi energy level lies between the first and the second excited states. These two intersubband transitions were attributed to ground-to-first excited states and first-to-second excited states transitions. The energy separation between the latter two intersubband transitions was found to increase as the well width is increased. The fact that two intersubband transitions were observed in certain samples may suggest that specially designed quantum wells can be used for two color long wavelength infrared detectors.

Graphene-based dual-band independently tunable infrared absorber

Nanoscale ◽  
2018 ◽  
Vol 10 (33) ◽  
pp. 15564-15570 ◽  
Author(s):  
Peng Sun ◽  
Chenglong You ◽  
Amirreza Mahigir ◽  
Tongtong Liu ◽  
Feng Xia ◽  
...  
Keyword(s):  
Energy Level ◽  
Resonant Frequency ◽  
Fermi Energy ◽  
Dual Band ◽  
Fermi Energy Level ◽  
P Absorption

Absorption peaks can independently tune each resonant frequency by only changing the Fermi energy level of one.

scholarly journals Investigation of dopant centres dominating the conduction process in the bulk of un-doped GaSb

2019 ◽  
Vol 13 (4) ◽  
pp. 315-327
Author(s):  
Megersa Wodajo Shura
Keyword(s):  
Energy Level ◽  
Hall Effect ◽  
Fermi Energy ◽  
Activation Energies ◽  
Acceptor Level ◽  
Level System ◽  
Fermi Energy Level ◽  
Majority Carrier ◽  
Temperature Regimes ◽  
Hall Effect Measurements

Abstract In this paper, first, the theoretical description of the effects of the dopant densities and the activation energies on the ionization densities, the chemical potentials corresponding to each dopant levels, the majority carrier densities and the Fermi-energy levels in one-acceptor-level system, highly compensated system and two-acceptor-level system are described in detail. Upon fitting the theoretical to the experimental results obtained by the temperature-dependent Hall effect measurements for three samples of un-doped GaSb, the dopant densities and the activation energies for a system with different dopants are investigated. The obtained results revealed that the dopant activation energy has less (no) effect on the Fermi-energy level and the majority carrier density in the highest temperature regimes. The doping density has also less (no) effect on the Fermi-energy level in the lowest temperature regimes. Finally, fitting of the theoretical to the experimental Hall effect measurements results confirmed the presence of three acceptor and one donor levels dominating the majority carrier densities at different temperature regions in all the samples of un-doped GaSb semiconductor.

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